Membrane touch control panel assembly for an appliance with a glass control panel

ABSTRACT

An appliance with a glass control panel is provided with a membrane touch control panel assembly which simulates the appearance of a glass capacitive touch panel, and which can tolerate relatively harsh temperature environments such as on the backsplash of a range.

BACKGROUND OF THE INVENTION

This invention relates to a membrane touch switch control panel assemblyfor appliances with glass control panels.

Use of glass control panels for appliances such as ranges and wall ovensis well known. Such appliances typically have electromechanical controlswith user manipulated control knobs projecting through holes in theglass. Such structural arrangements are inconvenient to clean and alsoallow soils to enter the area behind the control panel leading to anunsightly appearance and possibly contaminating the control circuitry.

In some instances capacitive touch panel arrays have been used in lieuof mechanical knobs and switches, enhancing appearance and cleanability.Such arrays can be fabricated directly on the glass panel which servesas the dielectric substrate, thereby providing a smooth surface with noopenings to collect food soils and a modern high tech appearance. Alsosuch arrays can withstand the relatively high temperature environment towhich range and oven controls are exposed. Capacitive touch switcharrays have been found to provide satisfactory performance and pleasingappearance. However, capacitive touch panels while mechanically simpleare electrically relatively complex and have a relatively high systemcost. Consequently, such controls generally are provided only onexpensive appliances positioned at the high end of the model line.

Membrane touch switch arrays, which have substantially less system costthan capacitive touch pad arrays, are used in refrigerator, dishwasher,microwave ovens, and laundry appliances which provide a less harshtemperature environment, since materials conventionally used in membranetouch switch arrays do not tolerate high temperatures well.

Therefore, a touch control panel for appliances which has the costadvantages of membrane switch panels and the appearance and temperaturetolerance advantage of capacitive touch control arrays would be highlydesirable.

It is therefore a primary object of the present invention to provide amembrane touch switch control panel assembly for an appliance whichprovide the appearance and cleanability and temperature tolerancebenefits of a capacitive touch panel array.

SUMMARY OF THE INVENTION

In accordance with the present invention an appliance with a glasscontrol panel is provided with a membrane touch switch control panelassembly which provides the smooth appearance, easy cleanability of aglass capacitive touch panel, and a higher temperature tolerance thanthat of conventional membrane switch array.

A laminated membrane switch array is disposed on the outer surface ofthe glass control panel. The glass panel has a hole formed therein toallow the ribbon cable for the membrane switch array to pass through thepanel to control circuitry positioned behind the panel. A bezelcircumscribes the switch array with an inner edge which overlappinglyengages the array at its periphery to hold the array in position on thepanel with its face exposed to permit user actuation of the membraneswitches. A gasket may be sandwiched between the bezel and the glasspanel to provide a seal therebetween. The outer graphics layer of themembrane switch array is formed of a flexible, resilient temperatureresistant material, preferably a hard coat polycarbonate material,capable of withstanding temperature in excess of 220° F.

BRIEF DESCRIPTION OF THE DRAWINGS

While the novel features of the invention are set forth withparticularity in the appended claims, the invention, both as toorganization and content, will be better understood and appreciatedalong with other objects and features thereof, from the followingdescription taken in conjunction with the drawings, in which:

FIG. 1 is a perspective view of the upper portion of a free-standingrange illustratively embodying the membrane touch control panel assemblyof the present invention;

FIG. 2 is an enlarged plan view of the touch panel portion of thecontrol panel of FIG. 1;

FIG. 3 is an exploded perspective view of the touch panel assemblyembodied in the range of FIG. 1;

FIG. 4 is a sectional view of the control panel for the range in FIG. 1taken along lines 4--4;

FIG. 5 is an exaggerated sectional view of a switch portion of thelaminated membrane switch array of FIG. 4 taken along line 5--5 of FIG.2; and

FIGS. 6A and 6B show details of the shorting electrode and switchingelectrodes for the segment of the switch array illustrated in FIG. 5.

DETAILED DESCRIPTION

Referrig now to the drawings and in particular to FIGS. 1-3, there isshown a free-standing range 10, with four conventional surface units 12,supported from cooktop surface 14, and an oven enclosed by oven door 16.Control knobs 18 for the surface units and oven controls comprising atouch switch array 20 are supported from the backsplash comprising glasspanel 22. In order to minimize the exposure of the touch switch array toradiant energy from the back two surface units, the switch array iscentered horizontally on panel 22 relative to the surface units. Viewingarea 23 on panel 22 exposes an electronic display disposed behind thepanel area shown in phantom at 24 in FIG. 3. This display may include areal time clock, an oven timer, and oven operating mode indicators andprompts for operation of the oven controls. As best seen in FIG. 2,touch switch array 20 includes a graphical overlay 25 with indiciaidentifying the location and function of the various touch switches.

As best seen in FIG. 5, membrane touch switch array 20 is a laminatedtouch switch array which, with the exception of the graphics layer 25 isof generally conventional construction. FIG. 5 is greatly expandedsectional view of that portion of array 20 comprising touch switch 26which is representative of the other touch switches in the membranetouch switch array 20. The thicknesses are exaggerated for clarity.

Because of the harsh temperature environment due to the proximity of thecontrol panel to the surface units, the graphics overlay for membraneswitch array requires a flexible, resilient material capable ofwithstanding the relatively high temperature environment at thebacksplash proximate the rear surface units. Temperature in this areacan be on the order of 220° F. or higher. Thus, suitable materials mustbe albe to withstand such temperatures. Materials conventionally usedwith membrane touch panel arrays cannot tolerate such temperatures. Onematerial found to have characteristics which meet the flexibility,resiliency and temperature requirements for range application is thehard coat polycarbonate material available from General Electric Companyunder the registered trademark Lexan. In the illustrative embodimentgraphics overlay layer 25 is formed of Lexan hard coat polycarbonatematerial with thickness on the order of .015 inches.

The remaining structure of the membrane switch array is generallyconventional in nature and will be only briefly described. A layer ofaluminum foil 28 on the order of 0.35 mils in thickness serves as anelectrostatic shield for the switch array. As best seen in FIGS. 6A and6B, switch 26 comprises a pair of printed circuit electrodes or contacts30 and 32 formed on switch layer 34, and a shorting contact or electrode36 formed on switch layer 38. Switch layers 34 and 38 are formed ofpolyester material. The conductive patterns for the switch contacts aredeposited on the circuit boards using conventional printed circuittechniques. Each of contacts 30 and 32 have a plurality of fingersinterleaved with and spaced apart from the fingers from the othercontact. Shorting contact 36 is disposed in juxtaposition with contacts30 and 32. Insulating spacers 40 between circuit boards 34 and 38establish a gap between contact 36 and contacts 30 and 32. Switch 26 isactuated by pressing the switch area above contact 36, which urgescontact 36 into electrical contact across contacts 30 and 32 therebyclosing the switch.

As best seen in FIGS. 3-5, the touch panel assembly comprises membraneswitch array 20 and bezel 42. Optional gasket 44 provides a seal betweenbezel 42 and panel 22; however, it has been found that bezel 42 can besufficiently secured to panel 22 to provde an adequate sealtherebetween. Thus, gasket 44 is not necessary for satisfactoryperformance. Membrane switch array 20 is secured on the outer surface ofglass panel 22 by a plastic bezel 42 which circumscribes membrane switcharray 26. Bezel 42 includes a rectangular opening 46 to accommodateswitch array 20. A flange 48 formed along the inner edge of bezel 42surrounding rectangular opening 46, overlappingly engages the peripheraledges of switch array 20 to retain array 20 in position on control panel22. A second opening 50 in bezel 42 exposes viewing area 23 for thedigital display (not shown) mounted behind the glass panel and visibletherethrough.

A plurality of mounting studs 52 project from bezel 42. A plurality ofsmall holes 54 are formed in glass panel 22 for receiving studs 52 tolocate bezel 42 on panel 22. Optional gasket 44 is shown sandwichedbetween bezel 42 and glass panel 22 to provide a seal therebetween.Openings 56 in gasket 44 align with openings 54 in panel 22 toaccommodate mounting studs 52.

Membrane switch panel array 20 includes a ribbon cable 58 which carriesconductors for connecting the touch panel array to control circuitry(not shown) disposed behind panel 22. Glass panel 22 has an opening 60to accommodate ribbon cable 58 which passes therethrough to the controlcircuitry behind the panel.

As best seen in FIG. 4, mounting studs 52 project through the glasspanel. Fastening means such as push-on lock nuts 62 attached to the endsof studs 52 behind panel 22 snugly secure bezel 42 against gasket 44 andthe periphery of membrane switch array 20.

When fully assembled, bezel 42 appears as simply a trim piece on theglass surface to set off the touch switches, the overall effect being tosimulate the appearance of a capacitive touch panel.

While in accordance with the Patent Statutes a specific embodiment ofthe present invention has been illustrated and described herein, it isrealized that numerous modifications and changes will occur to thoseskilled in the art. For example, the touch panel assembly is describedfor use in a free-standing range. However, the touch panel assembly canbe readily employed with other appliances equipped with glass controlpanels such as, for example, built-in wall ovens. It is therefore to beunderstood that the appended claims are intended to cover allmodifications and changes as fall within the true spirit and scope ofthe invention.

What is claimed is:
 1. In a cooking appliance having a plurality ofsurface units and a glass control panel disposed proximate the surfaceunits a membrane touch switch control panel assembly comprising:alaminated membrane switch array disposed on the outer surface of theglass control panel having a ribbon cable for connecting said switcharray to control the circuitry disposed behind the glass control panel,the glass control panel having a hole formed therein to allow saidribbon cable to pass therethrough; a bezel which circumscribes saidswitch array having an inner edge which overlappingly engages saidswitch array at the periphery thereof; means for securing said bezel tothe outer surface of the glass control panel, said switch array beingsandwiched between said inner edge of said bezel and outer face of theglass control panel; whereby said membrane touch switch control panelassembly simulates the appearance of a glass capacitive touch panel. 2.The membrane touch switch control panel assembly of claim 1 wherein theglass control panel has formed therein a plurality of holes and whereinsaid securing means comprises mounting studs projecting from the innersurface of said bezel for receiving said studs thereby locating saidswitch array on the glass control panel.
 3. The membrane touch switchcontrol panel assembly of claim 1 wherein said switch array includes anouter graphics layer comprising a flexible resilient material capable ofwithstanding temperatures in excess of 220° F.
 4. The membrane touchswitch control panel assembly of claim 3 wherein said outer graphicslayer is formed of hard coat polycarbonate material.
 5. A membrane touchswitch control panel assembly for a cooking appliance having a pluralityof surface units and a glass control panel disposed proximate at leastone of the surface units, said assembly comprising:a laminated membraneswitch array disposed on the outer surface of the glass control panel;said switch array including an outer appearance graphics layer formed ofa flexible resilient material capable of withstanding temperatures inexcess of 220° F.; mounting means circumscribing said switch array forsealingly securing said switch array at the edges thereof to the glasscontrol panel; said outer appearance graphics layer and said mountingmeans together simulating the appearance of a glass capacitive touchpanel.
 6. The membrane touch switch control panel assembly of claim 5wherein said mounting means comprises a bezel which circumscribes saidswitch array having an inner edge which overlappingly engages saidswitch array at the periphery thereof, said bezel having mounting studsprojecting from the inner surface thereof, the glass control panelhaving a plurality of holes formed therein for receiving said mountingstuds to locate said bezel and said switch array and secure said bezelto the glass control panel.
 7. The membrane touch switch control panelassembly of claim 6 wherein said switch array includes a ribbon cablefor conecting said switch array to control circuitry disposed remotefrom said switch array, and wherein the glass control panel has formedtherein a hole for permitting said cable to pass therethrough.
 8. Themembrane touch switch control panel assembly of claim 7, wherein saidouter appearance graphics layer is formed of hard coat polycarbonatematerial.